To start out with, both the movie and the manga have a scene where Sugimura is killed by Kotohiki. In the manga, Kotohiki attempts to kill Sugimura, but fails. The manga builds off of this fact and goes to a really insane unrealistic fight scene afterwards against Kiriyama (albeit entertaining). However, the impact of Sugimura's death in the hands of Kotohiki is a lot heavier than you'd expect. On the flip side, the manga does have Kotohiki die right in front of Sugimura, which makes his story just as if not more tragic, so you could argue that side.
The reason why I don't like the movie compared to the manga and novel is that it heavily simplifies the relationship between Mimura, Iijima, and Seto. In the movie, they're all good friends and everything, but in the manga and novel, it shows a falling out between Mimura and Iijima, ultimately resulting in the death of Iijima. This in turn deepens the relationship between Mimura and Seto, making the scene where Seto is killed more tragic. The manga goes into a bit more detail here (though a bit over the top) than the book.
Another advantage that the book has over the manga and the movie is the small talk. The books goes into a lot of detail about how each character is feeling during the story and does a very good job at describing scenes (for example, when Oda dies, the book describes his head in the helmet to be like a bowl of porridge filled with blood and brains I think). In a sense, you could argue that in some scenes that book is even more gruesome than the manga and movie.
Kuramoto and Yahagi also commit suicide in the film. Not as tragic as when they were killed by Souma in the book/manga.
I liked Sasagawa's death in the manga more than the book. It engaged in the "last moments of his life" scene and I think the manga did a better job of explaining it than the book.
Takiguchi's death was also a lot more interesting in the book than the manga. His death was entirely cheapened in the movie